1. Field of the Invention
This invention relates to a composition of polyamide, polyethylene and an ionic copolymer.
2. Description of the Prior Art
The blending of polyamide (nylon) with polyolefin is known. These two materials are regarded as incompatible due to their difference in structure, crystallinity and chemical component groups. One way to achieve compatibility in a blend of polyamide and polyolefin is to add an additional component. Several patents are concerned with improvement of the compatibility of polyamide-polyolefin blends.
U.S. Pat. Nos. 3,373,222; 3,373,224 and 3,873,667 disclose blends of polyamide, polyolefins such as polyethylene and a third component which enables the first two components to be compatible. In U.S. Pat. No. 3,373,222 the third component is a carboxylated linear polyethylene having an acid number of 2.75 to 50. The third component of U.S. Pat. No. 3,373,224 is an ionic copolymer partially neutralized by sodium ions. U.S. Pat. No. 3,873,667 discloses as a compatibilizing material an ionic copolymer partially neutralized by metal ions. The three patents relate to compositions which possess resistance to the permeation of fluids and gases. In these patents it is necessary to obtain these physical properties by controlling the amount or ratio of polyamide and polyolefin present in the blend. These patents do not disclose a composition in which the polyamide content is as great as 60 percent by weight or a polyolefin content less than 40 percent by weight.
Another prior art teaching, U.S. Pat. No. 3,845,163 discloses a two-component blend of polyamide in an amount of 50 to 99 percent by weight, with the remainder being an acid-containing olefin polymer in which the acid is an .alpha.,.beta.-ethylenically unsaturated carboxylic acid in which at least 10 percent of acid groups have been neutralized with metal ions. The blend provides higher toughness, particularly weld-line toughness, in molded articles in comparision to a blend of polyamide and an acid containing olefin copolymer (which does not contain metal ions).
U.S. Ser. No. 523,467, and now U.S. Pat. No. 3,963,799, relates to polymer blends of polyamide and polyethylene, the former in a predominant amount. A minor amount of graft copolymer is present in the blend, the graft copolymer consisting essentially of a trunk copolymer derived from ethylene and a comonomer providing amine-reactive sites, and polycaprolactam side chains having an average degree of polymerization of about 5 to 30 linked to the reactive sites through amide. The graft copolymer materially aids in permitting a fine grain dispersion of the polyethylene component in the polyamide.